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Discussion Starter · #1 ·
Okay, I've got one. Lets say you had a 98 tahoe (5.7 Vortec) 4x4, and it was going to be used off road only, can you do away with the cat. converter? will it run right? will the check engine light stay on? is there a way around this?
 

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The only reason the light should come on is if you have an o2 sensor behind the cat. I can't find my book right now, but I'm pretty sure that's not the case. Today's cats are not that restrictive, so removing it will only decrease a small amount of weight, and perhaps ease exhaust restriction a little. Otherwise the only other effect it would have is helping to kill off fresh air.

I don't see how you'd have a problem.
 

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The only reason the light should come on is if you have an o2 sensor behind the cat. I can't find my book right now, but I'm pretty sure that's not the case. Today's cats are not that restrictive, so removing it will only decrease a small amount of weight, and perhaps ease exhaust restriction a little. Otherwise the only other effect it would have is helping to kill off fresh air.

I don't see how you'd have a problem.
completely agree.
 

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You could be opening a can of worms

You didn't mention why you needed to remove the catalytic converter. Often people think there is an immediate improvement in perfromance, but this is not necessarily true. Corvette's and Viper's have catalytic converters and they aren't short on HP. In fact your truck may run worse without the cat. I haven't removed a cat before, but I have modified intake and exhaust on vehicles that have required adjustments afterwards to run correctly.

I remember a trans am that I just flipped the air cleaner lid upside down to improve airflow to the carb (the sound of the secondaries opening is so cool) and it ran worse. Why? Because the air fuel mixture was optimized with the restrictive lid in place.

You could try removing the cat, but be prepared to up the ante with some expensive mods and be sure to hang onto the cat because you may have to put it back.

From: http://www.randomtechnology.com/universal.html

"Computerized engine management systems are precisely calibrated to deliver optimum performance with an exhaust system that offers some amount backpressure. When backpressure is all but eliminated, air/fuel mixtures can easily become too lean to allow an engine to produce maximum power. Reestablishing optimum air/fuel ratios requires a custom computer calibration, altered fuel pressure or both."
 

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You didn't mention why you needed to remove the catalytic converter. Often people think there is an immediate improvement in perfromance, but this is not necessarily true. Corvette's and Viper's have catalytic converters and they aren't short on HP. In fact your truck may run worse without the cat. I haven't removed a cat before, but I have modified intake and exhaust on vehicles that have required adjustments afterwards to run correctly.

I remember a trans am that I just flipped the air cleaner lid upside down to improve airflow to the carb (the sound of the secondaries opening is so cool) and it ran worse. Why? Because the air fuel mixture was optimized with the restrictive lid in place.

You could try removing the cat, but be prepared to up the ante with some expensive mods and be sure to hang onto the cat because you may have to put it back.

From: http://www.randomtechnology.com/universal.html

"Computerized engine management systems are precisely calibrated to deliver optimum performance with an exhaust system that offers some amount backpressure. When backpressure is all but eliminated, air/fuel mixtures can easily become too lean to allow an engine to produce maximum power. Reestablishing optimum air/fuel ratios requires a custom computer calibration, altered fuel pressure or both."
This is a good point, regarding todays newer computer controlled engines.

To be honest I've never heard of anyone having their engine run worse from flipping their carb air cleaner cover. I've heard people get worse gas mileage, since they tend to stand on the throttle more because of the sound. I'm not saying it's impossible, just never heard that one before.
 

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Discussion Starter · #6 ·
Okay, my Tahoe is niether a Corvette or a Viper. Now I am sure we are all adults here and any gearhead knows that more flow is good whether you are talking about fuel, air, or exhaust, this also applies to everything from a go-cart to a formula-one racecar, and yes there are tons of aftermarket mods for Vettes and Vipers for people who race them, they tend to remove all smog equipment when they do that. My reason for wanting to remove my cat is simple, I don't really want to shell out the bucks they are wanting for one, they run from just under a hundred to almost three-hundred. My muffler is about to be replaced along with all of the pipes comming off the Cat, which I am thinking is due for replacement any time, and might already be partially clogged which is not that noticeable due to the fact I have big rust holes in the pipe leading to it. I dont know if any of this makes sense, but I am going to be out a couple hundred $$ on a Flowmaster, and new pipes throughout the length of my Tahoe as well as labor, I am only trying to keep from addind another couple hundred to it. I was looking at an 02 simulator on the net it is only like $25 I wonder if it works? It is supposed to keep high flow exhaust from throwing a check engine code, causing the ECM to maladjust the fuel air mixture, which is what I am wondering if I will run into. If anyone knows if there is an 02 sensor behind the cat., let me know.
 

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Okay, my Tahoe is niether a Corvette or a Viper. Now I am sure we are all adults here and any gearhead knows that more flow is good whether you are talking about fuel, air, or exhaust, this also applies to everything from a go-cart to a formula-one racecar, and yes there are tons of aftermarket mods for Vettes and Vipers for people who race them, they tend to remove all smog equipment when they do that. My reason for wanting to remove my cat is simple, I don't really want to shell out the bucks they are wanting for one, they run from just under a hundred to almost three-hundred. My muffler is about to be replaced along with all of the pipes comming off the Cat, which I am thinking is due for replacement any time, and might already be partially clogged which is not that noticeable due to the fact I have big rust holes in the pipe leading to it. I dont know if any of this makes sense, but I am going to be out a couple hundred $$ on a Flowmaster, and new pipes throughout the length of my Tahoe as well as labor, I am only trying to keep from addind another couple hundred to it. I was looking at an 02 simulator on the net it is only like $25 I wonder if it works? It is supposed to keep high flow exhaust from throwing a check engine code, causing the ECM to maladjust the fuel air mixture, which is what I am wondering if I will run into. If anyone knows if there is an 02 sensor behind the cat., let me know.
According to what I'm seeing you have four O2 sensors.
2 pre-converter, and 2 post converter.
The two after the converters don't detect high flow exhaust, they measure the ratio, and that should stay within a certain range regardless of moving 100cfm, or 1000cfm of exhaust.
However they are probably a narrow band O2 sensor, which means they will be tuned for a much cleaner output after the cat. So you probably will need the simulators, to keep the SES light from coming on.

I cannot speak to whether or not they work.
 

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Discussion Starter · #8 ·
two post converter? well I guess I will need two of 'em. A friend tells me his '98 silverado has no cat, and no simulators, never had any codes and actually gets higher mpg, but no noticeable perf gain, I am going to try it that way first... stay TUNED
 

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I'm seeing that you should have two O2 sensors after the cat. But the best way to be sure, is to do a quick visual inspection.
According to my book you should have two cats. One on each side of the Y pipe.
Keep us posted.
 
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